This invention relates generally to remote control of electrical apparatus and particularly to apparatus fabricated in circuit board arrangements. Even more specifically, this invention relates to control systems that afford multiple user control from different locations.
The background of the present invention will be more fully understood with reference to FIGS. 1-5. Referring now to FIG. 1, there is shown a basic control arrangement for controlling a device 10 by an electrical switch 12. Switch 12 is an operators control that may be located in a remote control console some distance from device 10 to be controlled. In one embodiment, device 10 performs one of N mutually exclusive functions in response to the state or position of switch 12 selected by an operator. For example, device 10 may be a radio transmitter and switch 12 may be used to select its operating channel. The transmitter is intended to transmit on only one channel at a time, hence the channel selection controlled by switch 12 is mutually exclusive.
The basic control arrangement shown in FIG. 1 includes a common line 14 coupled to a poll 16 of switch 12. The specific mutually exclusive functions of device 10 are selected by coupling poll 16 of switch 12 to one of N switch lines 18 (18-1 . . . 18-N). Switch 12 can be remotely located at an operator remote control console or control panel. A multiple wire cable interconnects switch 12 via lines 14 and 18 to device 10. Such a control arrangement is adequate for a single operator controlling device 10 from a single location.
However, if it is desired to provide a second operator's control point, switch 12 must be replaced with two switches, one for each operator. FIG. 2 illustrates an attempt to expand the arrangement shown in FIG. 1 to one affording control to two operators at different control points. The single switch of the FIG. 1 arrangement is replaced by two switches in parallel.
Referring now to FIG. 2, there is shown a multiple operator control arrangement. In this particular case, only four switch lines 18 (18-1 . . . 18-4) are shown for simplicity. However, any number of switch lines can be utilized. Common line 14 is coupled to the polls 20 and 22 of two switches 24 and 26, respectively. Each of switches 24 and 26 performs a function identical to that performed by switch 12 in FIG. 1. Switch 24 includes throws coupled one each to switch lines 18-1 . . . 18-4. Similarly, switch 26 includes throws coupled one each to switch lines 18-1 . . . 18-4. Thus, switches 24 and 26 are in parallel with one another and control can be exercised by the operator of either of these switches. Even though only two switches 24 and 26 are shown, this arrangement is naturally extendable to an even greater number of switches and operators. The problem with the arrangement shown in FIG. 2 is that multiple and conflicting control commands may be requested by different users. Such a situation is illustrated by the switch positions illustrated in the figure. As illustrated in FIG. 2, switch 24 shows its poll 20 coupled to switch line 18-1, while switch 26 shows its poll 22 coupled to switch line 18-3. If device 10 to be controlled were a radio transmitter, and switches 24 and 26 were channel select switches, the transmitter would be receiving conflicting commands to transmit on the frequencies designated by both switch line 18-1 and switch line 18-3. Such an arrangement is unacceptable for obvious reasons. One approach to overcome the difficulties associated with the FIG. 2 control arrangement is illustrated by FIG. 3.
Referring now FIG. 3, there is shown a control arrangement providing multiple operator control of device 10. The arrangement shown in FIG. 3 solves the problem of conflicting commands from multiple operator controls. In this arrangement, the contacts of each of rotary switches 24 and 26, shown in FIG. 2, are replaced by momentary action switches 30 and 32 respectively. Momentary action switches 30 include switches 30-1 . . . 30-4, and momentary action switches 32 include switches 32-1 . . . 32-4. Each of momentary action switches 30 couples common line 14 to one of switch lines 18-1 . . . 18-4. Similarly, each of momentary action switches 32 couples common line 14 to one of switch lines 18-1 . . . 18-4. Thus, each of momentary action switches 30 is in pallel with its corresponding momentary action switch 32, i.e., switch 30-1 is in parallel with switch 32-1, etc.
Memory elements 36-1 . . . 36-4 are interposed along switch lines 18-1 . . . 18-4, respectively between switches 30 and 32 and device 10. Memory element 36-1 is interposed along switch line 18-1, memory element 36-2 is interposed along switch 18-2, etc. The load and store function of all of memory elements 36 is controlled by a memory control line 38. The term Load means to acquire new information and the term Store means to retain information previously acquired. Memory elements 36 are shown schematically and are intended to include a wide variety of memory elements, depending upon the particular application in which they are utilized. For example, memory elements 36 may be latching relays, in which case the load/store function would be referred to as latch/unlatched function. For electronic applications, memory elements 36 might be flip-flops. In such cases, the load/store function would be referred to as set/reset. For the purposes of the present discussion, all such specific implementations for memory elements 36 are considered to be identical. A control circuit 40 controls the load/store function of memory elements 36 by impressing the appropriate signal onto memory control line 38. Control circuit 40 is coupled to each of switch lines 18 and detects the presence of a closure from any of switches 30 and 32. Upon detecting a switch closure, control circuit 40 causes memory elements 36 to reacquire the status of the signals at their respective inputs, i.e., the signals on switch lines 18.
If a first operator at a control console including momentary action switches 30 desires to implement a different function than the function currently in use, he simply actuates the appropriate switch 30. Control circuit 40 detects the actuation and causes memory elements 36 to cycle through their load function. This establishes a new control signal which is transmitted to device 10 via lines 42 (42-1 . . . 42-4) coupling the outputs of memory elements 36 to control inputs of device 10. Any previous command is automatically lost or reset since all memory elements 36 are cycled to reacquire the status of the signal coupled thereto, and since switches 30 and 32 are momentary acting switches and which do not remain in constant contact with their respective switch lines. In essence, a switch line closure which is momentary on lines 18 is maintained constant on lines 42 by the action of memory elements 36. An operator at a control console including momentary action switches 32 can similarly change the previously implemented function for device 10.
When the control arrangement shown in FIG. 3 is applied to electronic circuits fabricated in circuit board arrangements, it has distinct disadvantages. In order to better understand these disadvantages, reference is made to FIGS. 4 and 5.
Referring now to FIG. 4, there is shown a typical circuit board implementation of the control arrangement shown in FIG. 1. A common method of packaging complex electronic systems is to partition the system into smaller segments or subsystems. Each subsystem is manufactured on its own circuit board. The various circuit board are mounted in a card cage. The circuit boards themselves plug into edge connector sockets on a back plane circuit board, also known as a mother board. Circuitry on the back plane board interconnects the other circuit boards attached thereto.
Specifically, in FIG. 4, a device 10 to be controlled, such as a radio transmitter, is fabricated on a device circuit board 50. Control connections 52 on device circuit board 50 interconnect with a set of terminals 54 on a back plane circuit board 58. Back plane circuit board 58 includes a set of wires 56 (56-1 . . . 56-5). Wires 56 couple, one each, the terminals 54 to a set of terminals 57 also located on back plane circuit board 58. Switch 12 is remotely located and is coupled to terminals 57 via common line 14 and switch lines 18. Common line 14 and switch lines 18 are coupled through terminals 57 to their respective wires 56 on a back plane circuit board 58.
In order to provide cost effective volume production of device 10, it is desirable to manufacture a single, standardized version of the device. Most applications of the device can be handled by simple control schemes such as that shown in FIG. 1 and in FIG. 4. However, a significant portion of applications will require complex controls with two or more operator consoles. Operator consoles may not be within sight or sound of each other, in which case the various operators will not know which position switch 12 is in unless a status feedback indication is given to each console. To provide such status feedback the control arrangement illustrated by FIG. 4 must be expanded to the arrangement shown in FIG. 5.
Referring to FIG. 5, there is shown a control arrangement providing status indicators to each operator. The control arrangement shown in FIG. 5, is similar to that shown in FIG. 3. However, it includes the required interconnections for circuit board fabrication and, in addition, shows the addition of indicator lights indicating the status of the function selected by the various switches. Thus, FIG. 5 illustrates the full implications of having multiple control points implemented with the basic control arrangement illustrated by FIG. 3. An operator at a first control console can request a function change by operating one of momentary action switches 30. Similarly, the operator of a second control console can request a function change by operating one of his momentary action switches 32. A set of indicators 60 at the first control console and 62 at the second control console indicate to the operators the function presently implemented by device 10.
In this FIG. 5 arrangement, device 10 is fabricated on a device circuit board 50. A control circuit 40 and memory elements 36 are fabricated on a control circuit board 60. A back plane circuit board 62 provides the appropriate wire interconnections for device circuit board 50, control circuit board 60, and for coupling the common line 14, switch lines 18 and a set of indicator lines 64. It is assumed, for the purpose of the arrangement shown in FIG. 5, that the memory elements 36 have relatively low power output capability, and therefore buffer amplifiers 66 (66-1 . . . 66-4) couple the outputs of the memory elements to indicators 60 and 62. Buffer amplifiers 66 also isolate the lines 42 and the memory elements from any extraneous signals which might couple through the indicator lights from power source V. For a system with N functions, 3 N connections to control board 60 are required.
It is assumed that semiconductor technology is used to implement memory elements 36 as opposed to relays. If memory elements 36 are implemented by relays or other devices not requiring isolation and if device 10 is not subject to false signals coupled through the indicators via lines 42 then the amplfiers are not needed and one set of the edge connectors on back plane circuit board 62 and control circuit board 60 can be eliminated. However, even if one set of connectors were eliminated, there would still be required 2 N connections for N switch lines.
In order to implement the FIG. 3 control arrangement in circuit board construction, it is necessary to construct a special back plane board 62 different from FIG. 4 and having many additional connections. Back plane board 62 can not be used for a simple system such as that shown in FIG. 4. Furthermore, cables used to connect the control consoles with back plane board 62 must have twice the number of wires and terminals as would be required by the implementation shown in FIG. 4. Furthermore, twice the number of wires and terminals are required on back plane circuit board 62 as would be required on back plane circuit board 58 shown in FIG. 4. The indicators cannot be connected directly to the switches since the signals at the switches are momentary in nature and therefore would not provide a proper indication of system status. The number of interconnections to the control circuit board 60 is approximately 3 N where N is the number of switch lines to each of switches 30 and 32. Each such connection has associated with it the cost of a socket and other interconnecting elements. For any but the smallest number of control functions, the number of connections required on the various circuit board becomes quite large and exceeds the number of connections that can be made available on a single card. This forces the design of a much larger system or control circuit implemented on plural boards. Either alternative is quite expensive. Thus, there is a need to provide a control arrangement for use with circuit board systems that minimizes the number of interconnecting wires and terminals on a back plane circuit board, while providing all desired control functions and feedback status.